In the Nostram's Scientific Encyclopedia (4th Ed.), the term stereoscope is defined on page 1741 as follows: "The sensation of depth of an object is due to binocular vision; that is, to the fact that two eyes do not each see exactly the same view. By taking two pictures with a camera moved a few inches--or with a double stereoscopic camera--two slightly different pictures are obtained. A stereoscope is a device by which each eye sees only one of the pictures and the same sensation of depth is obtained as with direct binocular vision."
In this treatise under the heading "Stereoscopic Photography" it is pointed out that in 1833 the British scientist Sir Charles Wheatstone is generally credited with the invention of the stereoscope. These devices were popular from the middle of the 19th century and remained so until advances in photography which occurred in the 20th century. Aside from polarized types of glasses, little attention appears to have been devoted to producing novel stereoscopic viewers in recent years.
So far as is known, most viewers involve looking at two side by side photographs in the manner referred to above, or viewing a single image with two different polarizations.
In recent years, with the tremendous popularity of televisions and VCRs, innumerable people find themselves watching the images which appear on the cathode ray tubes of a TV and/or VCR. Unfortunately, however, most images which appear on such tubes are not three dimensional. Consequently, viewers generally do not see any depth of the images with a result that much of the value of what can appear on the screen is lost.
What has been needed, therefore, is an inexpensive type of stereoptic viewer which can be widely distributed among TV and VCR watchers, with the object of enabling such watchers to enjoy more depth perception of images which appear on their screens.